M-Sn-Q (M = Zn, Cd; Q = S, Se) Compounds Templated by (Alkyl)ammonium Species: Synthesis, Crystal Structure, and Sr 2+ Adsorption Property.

Deep investigations on the synthetic and structural chemistry of heterometallic chalcogenidostannates bear fundamental significance for the establishment of the structure-property relationship that would offer guidance on the functional material innovation. Presented here are four ammonium- and/or alkylammonium-directed M-Sn-Q (M = Zn, Cd; Q = S, Se) compounds, namely, [NH 4 ] 7 [H 3 O] 3 Zn 4 Sn 4 S 17 ( 1 ), [NH 4 ] 5 [(CH 3 ) 2 NH 2 ]Zn 4 Sn 5 S 17 ( 2 ), [CH 3 CH 2 NH 3 ] 22 Zn 16 Sn 12 Se 51 (H 2 O) 4 ·16H 2 O ( 3 ), and [NH 4 ] 2 CdSnSe 4 ( 4 ). All four compounds were synthesized in deep eutectic solvents (DESs) or ethylamine aqueous solution, both of which function simultaneously as reaction media and structure-directing agents. Compound 1 consists of discrete P1-[Zn 4 Sn 4 S 17 ] 10- clusters templated by mixed [NH 4 ] + /[H 3 O] + cations. In compound 2 , such P1 clusters are bridged by Sn 4+ ions in a 4,4-connection mode to form a [Zn 4 Sn 5 S 17 ] n 6 n - framework with three types of cavities (I-III) varying in size. The two smaller cavities (I and II) accommodate NH 4 + while the larger one(III) is occupied by [(CH 3 ) 2 NH 2 ] + , reflecting the rational size-dependence of cations on cavities. Compound 3 features an [Zn 16 Sn 12 Se 51 (H 2 O) 4 ] n 22 n - open framework constructed from the 4,3-connection of P1-[Zn 4 Sn 4 Se 17 ] 10- clusters and {Zn(H 2 O)} 2+ bridges. This linkage mode contributes to a large cage-like subunit (inner dimension: 21.99 × 9.06 Å 2 ) and therefore an ultrahigh porosity that are occupied by [CH 3 CH 2 NH 3 ] + cations and water molecules (volume fraction: 57.7%). Compound 4 exists as a stacking of [CdSnSe 4 ] n 2 n - chains, which are composed of alternatively arranged {CdSe 4 } and {SnSe 4 } tetrahedra, in combination with [NH 4 ] + cations as both charge-compensating and space-filling agents. Detailed synthetic, structural, and topological analyses were performed on these solid materials, coupled with extensive investigations on their optical and thermal properties. Compound 3 exhibits an efficient Sr 2+ adsorption performance, featuring ultrafast kinetics (94.69% in 5 min), high removal rate (98.57% in 20 min) at equilibrium, and high capacity (104.17 ± 23.53 mg g -1 ).